CN113991611B - Switch power supply and protection circuit thereof - Google Patents
Switch power supply and protection circuit thereof Download PDFInfo
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- CN113991611B CN113991611B CN202111470200.XA CN202111470200A CN113991611B CN 113991611 B CN113991611 B CN 113991611B CN 202111470200 A CN202111470200 A CN 202111470200A CN 113991611 B CN113991611 B CN 113991611B
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- 230000002159 abnormal effect Effects 0.000 claims abstract description 32
- 238000004804 winding Methods 0.000 claims description 23
- 239000003990 capacitor Substances 0.000 claims description 18
- 238000001514 detection method Methods 0.000 claims description 10
- 230000000087 stabilizing effect Effects 0.000 claims description 7
- 208000031361 Hiccup Diseases 0.000 abstract description 39
- 238000000034 method Methods 0.000 abstract description 16
- 230000002035 prolonged effect Effects 0.000 abstract description 8
- 102100036285 25-hydroxyvitamin D-1 alpha hydroxylase, mitochondrial Human genes 0.000 description 12
- 101000875403 Homo sapiens 25-hydroxyvitamin D-1 alpha hydroxylase, mitochondrial Proteins 0.000 description 12
- 238000009825 accumulation Methods 0.000 description 6
- 238000006243 chemical reaction Methods 0.000 description 6
- 238000010586 diagram Methods 0.000 description 5
- 238000007789 sealing Methods 0.000 description 4
- 230000005284 excitation Effects 0.000 description 2
- 238000001914 filtration Methods 0.000 description 2
- 230000006641 stabilisation Effects 0.000 description 2
- 238000011105 stabilization Methods 0.000 description 2
- 230000005856 abnormality Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000000750 progressive effect Effects 0.000 description 1
Classifications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/10—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers
- H02H7/12—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/02—Details
- H02H3/06—Details with automatic reconnection
- H02H3/063—Details concerning the co-operation of many similar arrangements, e.g. in a network
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Dc-Dc Converters (AREA)
Abstract
The invention provides a switch power supply and a protection circuit thereof, wherein the protection circuit is arranged between a power supply pin of a control chip in the switch power supply and the ground through a pull-down execution unit; when the switching power supply has abnormal output faults, the pull-down control unit controls the pull-down execution unit to switch into a passage, and then the voltage of the power supply pin of the control chip is pulled down to the ground, so that the power supply pin of the control chip is charged from 0V until the starting point of the control chip is ended in the hiccup protection mode each time; compared with the charging process from the under-voltage protection point to the starting point of the control chip in the prior art, the hiccup period is obviously prolonged, and the damage of the power device caused by the fact that the hiccup period is too short due to the fact that the power device is accumulated due to the fact that the power device is started frequently can be avoided.
Description
Technical Field
The invention relates to the technical field of power electronics, in particular to a switching power supply and a protection circuit thereof.
Background
The switching power supply is an AC-DC or DC-DC conversion unit, and is widely used in industrial fields due to its high efficiency, small size, and high reliability. The switch power supply is used as an auxiliary power supply unit of the system, and the stability and reliability of the switch power supply are of great importance, so that when the output of the switch power supply has abnormal faults such as overcurrent, short circuit, overvoltage and the like, the switch power supply needs to be ensured to be protected rapidly and reliably.
In the existing switching power supply, when detecting that the switching power supply has the abnormal output fault, a control chip of the switching power supply performs wave sealing treatment, so that the switching power supply stops working and further stops outputting, and meanwhile, the power supply connected with a VDD pin of the control chip is disconnected, and then the VDD power supply voltage is continuously reduced; when the VDD power supply voltage drops to the under-voltage protection point VDD of the control chip UVLO After that, the switching power supply is turned off and enters a hiccup protection mode (Hipcup). If the switching power supply input is not powered down, the switching power supply will restart, and the VDD supply voltage is from VDD UVLO Charged to the starting point VDD ON Then, the control chip restarts to work, and when the control chip detects that the abnormal output fault of the switching power supply is not relieved, the control chip seals the wave again; this is repeated until the output abnormality is resolved. Under normal conditions, the switching power supply enters a hiccup protection mode, and power limitation when the switching power supply has abnormal output faults can be achieved, so that power devices (a primary side MOS tube and a secondary side diode) in the switching power supply are protected from being damaged due to overstress or overheat.
However, in practical application, in the hiccup protection mode, the hiccup period, that is, the time interval between two startup of the switching power supply is usually shorter; especially in high voltage input situations, the VDD supply voltage can quickly charge to VDD ON . For a high-voltage input high-power switching power supply, the hiccup period is too short, so that a power device of the high-voltage input high-power switching power supply is easily damaged due to the fact that final heat accumulation is frequently started in a hiccup protection mode.
Disclosure of Invention
In view of the above, the present invention provides a switching power supply and a protection circuit thereof, so as to prolong the hiccup period in the hiccup protection mode and avoid damage caused by final heat accumulation of the power device due to frequent start-up.
In order to achieve the above object, the embodiment of the present invention provides the following technical solutions:
the first aspect of the present invention provides a protection circuit for a switching power supply, comprising: the device comprises a pull-down execution unit, a pull-down control unit and a pull-down power supply unit; wherein:
the pull-down execution unit is arranged between a power supply pin of a control chip in the switching power supply and the ground;
the output end of the pull-down control unit is connected with the control end of the pull-down execution unit and is used for controlling the pull-down execution unit to switch into a passage and maintaining a preset duration when the switching power supply has an abnormal output fault;
the pull-down power supply unit is used for supplying power to the protection circuit.
Optionally, the pull-down execution unit includes: the first resistor, the second resistor and the first switch tube;
one end of the first resistor is connected with a power supply pin of the control chip;
the other end of the first resistor is connected with the input end of the first switch tube;
the output end of the first switch tube is grounded;
the first switching tube control end is used as a control end of the pull-down execution unit;
the second resistor is arranged between the control end and the output end of the first switching tube.
Optionally, the pull-down control unit includes: the third resistor, the fourth resistor and the second switch tube;
one end of the third resistor receives the power supply voltage output by the pull-down power supply unit;
the other end of the third resistor is connected with the input end of the second switching tube, and the connection point is used as the output end of the pull-down control unit;
the output end of the second switch tube is grounded;
the second switching tube control end receives a shutdown/fault signal; when the switching power supply has abnormal output faults, the shutdown/fault signal controls the second switching tube to be switched off;
the fourth resistor is arranged between the control end and the output end of the second switching tube.
Optionally, the pull-down control unit includes: a fifth resistor, a sixth resistor, and a comparator;
the output end of the comparator is used as the output end of the pull-down control unit;
the positive input end of the comparator is connected with one end of the fifth resistor and one end of the sixth resistor;
the other end of the fifth resistor receives the power supply voltage output by the pull-down power supply unit, and the other end of the sixth resistor is grounded;
the negative input end of the comparator receives a shutdown/fault signal; when the switching power supply has abnormal output faults, the shutdown/fault signal enables the comparator to output a conduction control signal.
Optionally, the shutdown/fault signal is derived from: and the shutdown state pin of the control chip or the shutdown state detection circuit of the switching power supply.
Optionally, the pull-down power supply unit is used for taking power from an auxiliary winding of a switching transformer in the switching power supply.
Optionally, the pull-down power supply unit and a power supply pin of the control chip take power from the same auxiliary winding.
Optionally, the pull-down power supply unit includes: a diode and a capacitor;
the anode of the diode receives the power supply voltage of the auxiliary winding;
the cathode of the diode is grounded through the capacitor;
the negative electrode of the diode provides a supply voltage for the pull-down control unit.
Optionally, a voltage stabilizing circuit is further arranged between the pull-down power supply unit and the auxiliary winding.
The second aspect of the present invention also provides a switching power supply, comprising: a main circuit, a control chip, a detection circuit, and a protection circuit for a switching power supply according to any one of the first to fourth aspects; wherein:
the detection circuit is used for detecting the voltage and/or the current of the input end and/or the output end of the main circuit and outputting the voltage and/or the current to the control chip;
the control chip is used for realizing control and protection of the main circuit;
the protection circuit is used for pulling down the voltage of the power supply pin of the control chip to the ground when the switching power supply has abnormal output faults.
The protection circuit of the switching power supply is arranged between a power supply pin of a control chip in the switching power supply and the ground through the pull-down execution unit; when the switching power supply has abnormal output faults, the pull-down control unit controls the pull-down execution unit to switch into a passage, and then pulls down the voltage of the power supply pin of the control chip to the ground, so that in the hiccup protection mode, after the voltage of the power supply pin of the control chip is pulled down to the ground for a preset time period, the power supply pin of the control chip is charged each time, and the charging is started from 0V until the starting point of the control chip is ended; compared with the charging process from the under-voltage protection point to the starting point in the prior art, the hiccup period is obviously prolonged, and damage to the power device caused by the fact that the hiccup period is too short due to the fact that the power device is accumulated due to the fact that the power device is started frequently and finally heated can be avoided.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following description will briefly explain the embodiments or the drawings to be used in the description of the prior art, and it is obvious that the drawings in the following description are only embodiments of the present invention, and that other drawings can be obtained according to the provided drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic structural diagram of a protection circuit of a switching power supply according to an embodiment of the present invention;
fig. 2 is a schematic diagram of a connection relationship between a power supply pin of a control chip and other circuits of a switching power supply according to an embodiment of the present invention;
fig. 3 and fig. 4 are two circuit diagrams of a protection circuit of a switching power supply according to an embodiment of the present invention;
FIG. 5 is a circuit diagram of a voltage stabilizing circuit according to an embodiment of the present invention;
fig. 6 is a schematic structural diagram of a switching power supply according to an embodiment of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In this application, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
The invention provides a protection circuit of a switching power supply, which is used for prolonging the hiccup period in a hiccup protection mode and avoiding damage caused by final heat accumulation of a power device due to frequent starting.
As shown in fig. 1, the protection circuit of the switching power supply includes: a pull-down execution unit 103, a pull-down control unit 102, and a pull-down power supply unit 101; wherein:
the pull-down execution unit 103 is arranged between a power supply pin VDD of a control chip in the switching power supply and the ground GND; when the pull-down execution unit 103 is off, the pull-down execution unit has no influence on the voltage at the power supply pin VDD, which is the voltage VDD1 provided by the power supply of the control chip; when the pull-down execution unit 103 is on, the voltage at the power supply pin VDD is pulled down to ground.
The output end of the pull-down control unit 102 is connected with the control end of the pull-down execution unit 103; when the switching power supply works normally, the pull-down control unit 102 does not send out instructions; however, when an output abnormal fault occurs in the switching power supply, for example, when an output abnormal fault such as an output overcurrent, a short circuit, and an overvoltage occurs, the pull-down control unit 102 sends a pull-down instruction Shutdown to the pull-down execution unit 103, and controls the pull-down execution unit 103 to switch to a path so as to pull down the voltage at the power supply pin VDD to the ground and maintain the preset duration.
The pull-down power supply unit 101 is used for supplying power to the protection circuit; it can store energy when the switching power supply works normally, and supply power to the pull-down control unit 102 when the power supply fails abnormally.
The specific working principle is as follows:
referring to fig. 2, when the control chip detects that the output abnormal fault occurs in the switching power supply, the control chip performs the wave-sealing process, that is, no PWM signal is sent to the MOS tube VT1 connected to the primary winding S1 of the switching transformer 201 in the main circuit of the switching power supply, so that the MOS tube VT1 stops working.
In the prior art, the operation of the MOS tube VT1 is needed to stop, so that the secondary winding S2 of the switching transformer stops outputting to the rear stage, and the auxiliary winding S3 stops maintaining the power supply of the power supply pin VDD of the control chip; then, along with the discharge of the external capacitor of the power supply pin VDD, the voltage VDD1 of the power supply pin VDD is continuously reduced; when the voltage of the power supply pin VDD drops to the undervoltage protection point VDD of the control chip UVLO And then, the switching power supply is powered off and enters a hiccup protection mode. In the case that the switching power supply input is not powered down, the power supply pin VDD of the control chip receives the power supply of the start-up circuit 202, and the voltage of the power supply pin VDD is from VDD UVLO Charged to the starting point VDD ON Then, the control chip restarts working, and when the control chip detects that the abnormal power output fault is not relieved, the control chip seals the wave again; this is repeated until the abnormal power output fault is resolved.
In this embodiment, when the control chip detects that the output abnormal fault occurs in the switching power supply, the pull-down control unit 102 controls the pull-down execution unit 103 to switch to a channel, so that the voltage at the power supply pin VDD is directly pulled down to the ground, that is, 0V, and further the control chip is caused to perform under-voltage protection, and enter a hiccup protection mode; then, the pull-down power supply unit 101 discharges, and after a preset period of time, the pull-down control unit 102 controls the pull-down execution unit 103 to resume the off state. In the case that the switching power supply input is not powered down, the power supply pin VDD of the control chip receives the power supply of the start-up circuit 202, and the voltage of the power supply pin VDD is charged from 0V to the start-up point VDD ON Then, the control chip restarts working, and when the control chip detects that the abnormal power output fault is not relieved, the control chip seals the wave again; this is repeated until the abnormal power output fault is resolved.
It can be seen that this embodiment not only enables the switching power supply to enter the hiccup protection mode,the power limitation for the abnormal output fault is realized, so that the MOS tube VT1 and a secondary diode (not shown in fig. 2) are protected from being damaged by overstress or overheat; in addition, in the hiccup protection mode, each time the charging process of the power supply pin VDD of the chip is controlled, the charging process is started from 0V to the starting point VDD ON Ending; compared with the prior art from the undervoltage protection point VDD UVLO To the starting point VDD ON In the charging process, the hiccup period is obviously prolonged, and damage to the power device caused by frequent starting and final heat accumulation due to the fact that the hiccup period is too short can be avoided.
It should be noted that there is a way in the prior art to lengthen the hiccup protection time by increasing the way in which the start-up resistor/capacitor of the start-up circuit 202 is implemented; however, the power-on time of the power supply is also prolonged by the mode, so that the use experience of a user is reduced, and even the power supply time sequence of the whole system is affected. The hiccup period of the protection circuit provided by the embodiment can be prolonged only in the hiccup protection mode, the normal starting time is not influenced, the influence on the power supply time sequence of the whole system is not brought, and popularization and application are facilitated.
On the basis of the above embodiment, referring to fig. 3, this embodiment provides a specific implementation form of the pull-down execution unit 103, which includes: the first resistor R1, the second resistor R2 and the first switching tube Q1; wherein:
one end of the first resistor R1 is connected with a power supply pin VDD of the control chip; the other end of the first resistor R1 is connected with the input end of the first switching tube Q1; the output end of the first switching tube Q1 is grounded GND; the control end of the first switching tube Q1 is used as the control end of the pull-down execution unit 103; the second resistor R2 is disposed between the control end and the output end of the first switching tube Q1.
In practical applications, the second resistor R2 may be connected in parallel with a capacitor, which is not shown in fig. 3; in addition, the first resistor R1 and the second resistor R2 may be series-parallel connection of a plurality of resistors, and their resistance values may be determined according to practical application environments, which are all within the protection scope of the present application.
In addition, for the pull-down control unit 102, there may be a plurality of implementation forms, and fig. 3 and fig. 4 are two specific examples, respectively; as shown in fig. 3, the pull-down control unit 102 includes: the third resistor R3, the fourth resistor R4 and the second switching tube Q2; wherein:
one end of the third resistor R3 receives the power supply voltage VDD2 output by the pull-down power supply unit 101; the other end of the third resistor R3 is connected with the input end of the second switching tube Q2, and the connection point is used as the output end of the pull-down control unit 102; the output end of the second switching tube Q2 is grounded GND; the control end of the second switching tube Q2 receives a shutdown/fault signal VREF; when the switching power supply has abnormal output faults, the shutdown/fault signal VREF controls the second switching tube Q2 to be switched off; the fourth resistor R4 is disposed between the control end and the output end of the second switching tube Q2.
Alternatively, as shown in fig. 4, the pull-down control unit 102 includes: a fifth resistor R5, a sixth resistor R6, and a comparator U1; wherein:
the output end of the comparator U1 is used as the output end of the pull-down control unit 102; the positive input end of the comparator U1 is connected with one end of the fifth resistor R5 and one end of the sixth resistor R6; the other end of the fifth resistor R5 receives the power supply voltage VDD2 output by the pull-down power supply unit 101, and the other end of the sixth resistor R6 is grounded to GND; the negative input end of the comparator U1 receives a shutdown/fault signal VREF; when the switching power supply has abnormal output faults, the shutdown/fault signal VREF enables the comparator U1 to output a conduction control signal.
It should be noted that, the control chip may have a power-off state pin, so as to directly output the power-off/fault signal VREF when it detects that the output abnormal fault of the switching power supply occurs, thereby controlling the pull-down execution unit 103 to switch to the channel. Or when the control chip does not have the shutdown state pin, whether the MOS tube VT1 stops working or not and whether the control chip is in an under-voltage shutdown state or not can be detected through an additionally arranged shutdown state detection circuit; the shutdown state detection circuit can specifically rectify a PWM signal output to the MOS tube VT1 by the control chip, then judge the voltage after rectification, and if the voltage is 0V, the switching power supply is indicated to have abnormal output faults, and the control chip is in a wave-sealing state.
It should be further noted that, the pull-down power supply unit 101 may be powered on the auxiliary winding of the switching transformer, such as S3 shown in fig. 2 to 4, that is, the pull-down power supply unit 101 and the power supply pin VDD of the control chip are powered on the same auxiliary winding S3; in practical applications, the pull-down power supply unit 101 may also be another independent auxiliary winding (not shown in the figure), and even other auxiliary power supplies may be used to supply power to the pull-down power supply unit 101; all are within the protection scope of the application and depend on the specific application environment.
As shown in fig. 3 and 4, the pull-down power supply unit 101 includes: a first diode D1 and a first capacitor C1; wherein the positive electrode of the first diode D1 receives a corresponding power supply voltage; the cathode of the first diode D1 is grounded GND through a first capacitor C1; the negative electrode of the first diode D1 supplies the power supply voltage VDD2 to the pull-down control unit 102. After the pull-down control unit 102 controls the pull-down execution unit 103 to switch to the on-state, along with the power failure of the auxiliary winding S3, the first capacitor C1 starts to discharge, and after a preset period of time, the power supply voltage VDD2 becomes a low level, so that the pull-down control unit 102 shown in fig. 3 or fig. 4 controls the pull-down execution unit 103 to recover to the off-state; that is, the preset time period may be changed by adjusting a specific parameter setting of the first capacitor C1. Similarly, the power supply 203 of the control chip includes: a second diode D2 and a second capacitor C2; wherein the positive electrode of the second diode D2 receives a corresponding power supply voltage; the cathode of the second diode D2 is grounded GND through a second capacitor C2; the cathode of the second diode D2 provides the power supply voltage VDD1 for the control chip. In fig. 3 and fig. 4, the auxiliary winding S3 is shown as providing the power supply voltage to the pull-down power supply unit 101 and the power supply 203 through the fourth diode D4 and the fourth capacitor C4.
Preferably, a voltage stabilizing circuit 204 is further provided between the pull-down power supply unit 101 and the auxiliary winding S3. The voltage stabilizing circuit 204 can stabilize the voltage provided by the auxiliary winding S3 to a fixed value required by a subsequent stage; it specifically includes that shown in fig. 5: the third switch tube Q3, the voltage reference chip TL 431U 1, the third capacitor C3, the seventh resistor R7, the eighth resistor R8, the ninth resistor R9 and the tenth resistor R10; the input end of the third switching tube Q3 is connected with one end of a seventh resistor R7, and the connection point is connected with the cathode of a fourth diode D4 connected with the same-name end of the auxiliary winding S3; a fourth capacitor C4 is also connected between the fourth diode D4 and the ground; the control end of the third switching tube Q3 is connected with the other end of the seventh resistor R7, one end of the third capacitor C3 and the negative electrode of the voltage reference chip TL 431U 1; the eighth resistor R8, the ninth resistor R9 and the tenth resistor R10 are sequentially connected in series, and the other end of the eighth resistor R8 is connected with the power supply 203 of the pull-down power supply unit 101 and the control chip; the other end of the tenth resistor R10 is grounded with the positive electrode of the voltage reference chip TL 431U 1; the other end of the third capacitor C3 is connected to the reference end of the voltage reference chip TL 431U 1 and the connection point of the ninth resistor R9 and the tenth resistor R10. Fig. 5 shows only one specific example of the voltage stabilizing method, but is not limited thereto.
The auxiliary winding S3 of the main power transformer outputs through the fourth diode D4 of the auxiliary winding, and can further perform voltage stabilization through the voltage stabilization link; the power supply voltage VDD1 is then supplied to the power supply pin VDD of the control chip through the power supply 203, and the power supply circuit VDD2 is also supplied to the pull-down control unit 102 through the pull-down power supply unit 101. This configuration can save the auxiliary winding, and can also make the power supply 203 and the pull-down power supply unit 101 share the same voltage stabilizing circuit 204, which is advantageous in reducing the cost, but is not limited thereto.
For the structure shown in fig. 3, the specific working principle is as follows:
when the switching power supply works normally, the Shutdown/fault signal VREF is at a high level, for example, 5V, at this time, the second switching tube Q2 is closed, no instruction is issued by the pull-down control unit 102, at this time, the Shutdown is a low level signal, so that the first switching tube Q1 in the pull-down execution unit 103 is opened, and no influence is exerted on the supply voltage VDD1 of the control chip.
When the switching power supply has abnormal output fault, the control chip seals the wave, and the power supply voltage VDD1 drops to VDD UVLO Then entering a hiccup protection mode; then, the shutdown/failure signal VREF switches to a low level, such asAnd 0V, the second switching tube Q2 is disconnected, the pull-down control unit 102 sends a pull-down instruction to the pull-down execution unit 103, at the moment, the Shutdown is a high-level signal, so that the first switching tube Q1 in the pull-down execution unit 103 is switched to be closed, an execution circuit is switched to be in a path, the power supply voltage VDD1 of the control chip is pulled down to 0V, and in the hiccup protection mode, the power supply voltage VDD1 of the control chip starts to charge from 0V, and the hiccup period is prolonged.
For the structure shown in fig. 4, the specific working principle is as follows:
the pull-down control unit 102 divides the power supply voltage VDD2 supplied from the pull-down power supply unit 101 to generate VDD2/K, K being a division coefficient.
When the switching power supply works normally, the Shutdown/fault signal VREF is at a high level, for example, 5V, and by reasonably selecting the voltage division coefficient K, VDD2/K is lower than VREF, for example, VDD 2/k=2.5v, vref=5v, so that the comparator U1 outputs a low level, no instruction is sent, at this time, the Shutdown is a low level signal, and further the first switching tube Q1 in the pull-down execution unit 103 is turned off, so that no influence is caused to the power supply voltage VDD1 of the control chip.
When the switching power supply has abnormal output fault, the control chip seals the wave, and the power supply voltage VDD1 drops to VDD UVLO Then entering a hiccup protection mode; then, the Shutdown/fault signal VREF is switched to a low level, for example, 0V, at this time VDD2/K is higher than VREF, for example, VDD 2/k=2.5v, vref=0v, so that the comparator U1 outputs a high level, and issues a pull-down instruction to the pull-down execution unit 103, at this time, the Shutdown is a high level signal, so that the first switching tube Q1 in the pull-down execution unit 103 is switched to be closed, the action of switching the execution circuit to the path is performed, the power supply voltage VDD1 of the control chip is pulled down to 0V, so that in the hiccup protection mode, the power supply voltage VDD1 of the control chip starts to charge from 0V, and the hiccup period is prolonged.
No matter which structure is adopted, the voltage of the power supply pin VDD of the control chip is charged from 0V to VDD in the hiccup protection mode under the condition that the input of the switching power supply is not powered down ON A kind of electronic device. This significantly increases the hiccup period compared to conventional schemes provided in the prior artThe problem that the high-voltage high-power switching power supply is damaged due to the fact that the hiccup period is too short and the final heat accumulation of the machine is frequently started under the hiccup protection mode can be effectively solved.
Another embodiment of the present invention further provides a switching power supply, as shown in fig. 6, which specifically includes: a main circuit, a control chip, a detection circuit (not shown in the figure) and a protection circuit. Wherein:
the main circuit can be an AC-DC conversion circuit, a DC-DC conversion circuit or an AC-AC conversion circuit, the topology of the main circuit can be in the forms of forward excitation, flyback excitation and the like, and in fig. 6, only the switching transformer 201 and the switching tube VT1 are shown, the homonymous ends of the transformer windings are not marked, and the network connected with the source electrode of the switching tube VT1 is not shown; the front stage of the switch transformer 201 may also be provided with corresponding input filtering, conversion topology, etc., and the rear stage of the switch transformer 201 may also be provided with corresponding conversion topology, output filtering, etc., which are all within the protection scope of the present application depending on the specific application environment; in addition, fig. 6 illustrates only the starting circuit 202, and is not limited thereto, and other schemes in the prior art may be adopted.
The detection circuit is used for detecting the voltage and/or the current of the input end and/or the output end of the main circuit and outputting the voltage and/or the current to the control chip for the control chip to calculate, process and the like.
The control chip is used for realizing control and protection of the main circuit; the control function at least comprises PWM control of a switching tube VT1 connected with a switching transformer in a main circuit, and the protection function at least comprises abnormal fault protection of overcurrent, short circuit, overvoltage and the like of the output of the main circuit.
The protection circuit is used for pulling down the voltage of the power supply pin VDD of the control chip to the ground when the switching power supply has abnormal output faults. The specific structure and working principle of the protection circuit are just described in the above embodiments, and are not described in detail herein.
By adding the protection circuit, when the power supply has abnormal output fault, the control chip can act after the wave-sealing treatment, so that the voltage of the power supply pin VDD of the control chip can be reducedPull down to ground (0V), enter hiccup protection mode with a hiccup period of charging from 0V to VDD ON The hiccup period is obviously prolonged, and damage to the power device caused by frequent starting and final heat accumulation due to the fact that the hiccup period is too short can be avoided.
In this specification, each embodiment is described in a progressive manner, and identical and similar parts of each embodiment are all referred to each other, and each embodiment mainly describes differences from other embodiments. In particular, for a system or system embodiment, since it is substantially similar to a method embodiment, the description is relatively simple, with reference to the description of the method embodiment being made in part. The systems and system embodiments described above are merely illustrative, wherein the elements illustrated as separate elements may or may not be physically separate, and the elements shown as elements may or may not be physical elements, may be located in one place, or may be distributed over a plurality of network elements. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of this embodiment. Those of ordinary skill in the art will understand and implement the present invention without undue burden.
Those of skill would further appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both, and that the various illustrative elements and steps are described above generally in terms of functionality in order to clearly illustrate the interchangeability of hardware and software. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.
The features described in the various embodiments of the present disclosure may be interchanged or combined with one another in the description of the disclosed embodiments to enable those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (10)
1. A protection circuit for a switching power supply, comprising: the device comprises a pull-down execution unit, a pull-down control unit and a pull-down power supply unit; wherein:
the pull-down execution unit is arranged between a power supply pin of a control chip in the switching power supply and the ground;
the output end of the pull-down control unit is connected with the control end of the pull-down execution unit and is used for controlling the pull-down execution unit to switch into a passage and maintaining a preset duration when the control chip detects that the switching power supply has abnormal output faults;
the pull-down power supply unit is used for supplying power to the protection circuit.
2. The protection circuit of a switching power supply according to claim 1, wherein the pull-down execution unit includes: the first resistor, the second resistor and the first switch tube;
one end of the first resistor is connected with a power supply pin of the control chip;
the other end of the first resistor is connected with the input end of the first switch tube;
the output end of the first switch tube is grounded;
the first switching tube control end is used as a control end of the pull-down execution unit;
the second resistor is arranged between the control end and the output end of the first switching tube.
3. The protection circuit of a switching power supply according to claim 1, wherein the pull-down control unit includes: the third resistor, the fourth resistor and the second switch tube;
one end of the third resistor receives the power supply voltage output by the pull-down power supply unit;
the other end of the third resistor is connected with the input end of the second switching tube, and the connection point is used as the output end of the pull-down control unit;
the output end of the second switch tube is grounded;
the second switching tube control end receives a shutdown/fault signal; when the switching power supply has abnormal output faults, the shutdown/fault signal controls the second switching tube to be switched off;
the fourth resistor is arranged between the control end and the output end of the second switching tube.
4. The protection circuit of a switching power supply according to claim 1, wherein the pull-down control unit includes: a fifth resistor, a sixth resistor, and a comparator;
the output end of the comparator is used as the output end of the pull-down control unit;
the positive input end of the comparator is connected with one end of the fifth resistor and one end of the sixth resistor;
the other end of the fifth resistor receives the power supply voltage output by the pull-down power supply unit, and the other end of the sixth resistor is grounded;
the negative input end of the comparator receives a shutdown/fault signal; when the switching power supply has abnormal output faults, the shutdown/fault signal enables the comparator to output a conduction control signal.
5. A protection circuit for a switching power supply according to claim 3 or 4, wherein the shutdown/fault signal is derived from: and the shutdown state pin of the control chip or the shutdown state detection circuit of the switching power supply.
6. The protection circuit of a switching power supply according to any one of claims 1 to 4, wherein the pull-down power supply unit takes power from an auxiliary winding of a switching transformer in the switching power supply.
7. The protection circuit of the switching power supply according to claim 6, wherein the pull-down power supply unit and a power supply pin of the control chip take power from the same auxiliary winding.
8. The protection circuit of a switching power supply according to claim 7, wherein the pull-down power supply unit includes: a diode and a capacitor;
the anode of the diode receives the power supply voltage of the auxiliary winding;
the cathode of the diode is grounded through the capacitor;
the negative electrode of the diode provides a supply voltage for the pull-down control unit.
9. The protection circuit of a switching power supply according to claim 6, wherein a voltage stabilizing circuit is further provided between the pull-down power supply unit and the auxiliary winding.
10. A switching power supply, comprising: a main circuit, a control chip, a detection circuit, and a protection circuit of the switching power supply according to any one of claims 1 to 9; wherein:
the detection circuit is used for detecting the voltage and/or the current of the input end and/or the output end of the main circuit and outputting the voltage and/or the current to the control chip;
the control chip is used for realizing control and protection of the main circuit;
the protection circuit is used for pulling down the voltage of the power supply pin of the control chip to the ground when the switching power supply has abnormal output faults.
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| CN202111470200.XA CN113991611B (en) | 2021-12-03 | 2021-12-03 | Switch power supply and protection circuit thereof |
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| CN202111470200.XA CN113991611B (en) | 2021-12-03 | 2021-12-03 | Switch power supply and protection circuit thereof |
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| CN101257258A (en) * | 2007-02-28 | 2008-09-03 | 群康科技(深圳)有限公司 | Switch power circuit |
| CN101847934A (en) * | 2010-05-07 | 2010-09-29 | Bcd半导体制造有限公司 | A kind of Switching Power Supply |
| CN105610314A (en) * | 2016-02-24 | 2016-05-25 | 广州金升阳科技有限公司 | Input undervoltage protection circuit and method |
| JP2016116298A (en) * | 2014-12-12 | 2016-06-23 | 富士通株式会社 | Power supply unit, power supply circuit and method for controlling power supply circuit |
| CN214958665U (en) * | 2021-05-17 | 2021-11-30 | 成都信息工程大学 | Hiccup protection circuit, power chip |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101257258A (en) * | 2007-02-28 | 2008-09-03 | 群康科技(深圳)有限公司 | Switch power circuit |
| CN101847934A (en) * | 2010-05-07 | 2010-09-29 | Bcd半导体制造有限公司 | A kind of Switching Power Supply |
| JP2016116298A (en) * | 2014-12-12 | 2016-06-23 | 富士通株式会社 | Power supply unit, power supply circuit and method for controlling power supply circuit |
| CN105610314A (en) * | 2016-02-24 | 2016-05-25 | 广州金升阳科技有限公司 | Input undervoltage protection circuit and method |
| CN214958665U (en) * | 2021-05-17 | 2021-11-30 | 成都信息工程大学 | Hiccup protection circuit, power chip |
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